Labour's Manurewa MP Louisa Wall is pursuing legal action against her own party over a nomination that was accepted to contest her seat.
The Labour Party sought advice from a Queen's Counsel about a nomination from Waitematā DHB board member Arena Williams that came in after the party deadline in early February.
The timing of the nomination being received and accepted is understood to be central to the legal action.
Labour Party president Claire Szabo said the party had taken care to follow its constitution in accordance with legal advice.
Wall, Williams and longtime electorate organiser Ian Dunwoodie have all been approved for candidate selection in the Auckland seat.
Wall, who has held the electorate since 2011 and last year won the seat by an 8000-vote majority, declined to comment when approached by RNZ.
Prime Minister and Labour leader Jacinda Ardern said things like selection processes are dealt with by the party, not her.
"Generally, they don't tend to interest the rest of New Zealand but usually are confined to the Labour Party and the local electorate.
"So those processes need to run their course - I'm not attempting to intervene in that," she said.